Plural stepping motor numerical feed control device

ABSTRACT

A numerical feed control device is disclosed in which a worktable is driven by a pair of pulse motors, each of which moves a different distance when actuated by a driving pulse. The two motors are mechanically coupled so that their respective movements are added together. A control system is provided for permitting the pulse motors to be selectively driven so that the resolution of the system can be adjusted, where resolution is defined as the movement of the work table for each driving pulse applied to the system. The control system includes decoding equipment for properly selecting resolution commands from input numerical instruction words, and a network of logic gates for appropriately driving the two pulse motors in response to a particular resolution command.

Uted States atent 1 Asano et all.

[451 Sept. 4, 1973 PLURAL STEPPlNG MOTOR NUMERICAL FEED CONTROL DEVICE[75] Inventors: Hiroaki Asano, Hekikai-gun,

Aichi-ken; Tsuyoshi Koide; Taisuke Kawamata, both of Kariya-shi,Aichi-ken, all of Japan [73] Assignee: Toyoda Koki Kabushiki Kaisha,

Aichi-ken, Japan [22] Filed: Jan. 4, 1971 [21] Appl. No.: 103,683

[56] References Cited UNITED STATES PATENTS l/195l Seid et al. 318/6039/1950 Fairbanks 318/8 5/1969 Leshey et a1 318/8 X Primary Examiner-T.E. Lynch Att0rney0blon, Fisher & Spivak [5 7 ABSTRACT A numerical feedcontrol device is disclosed in which a worktable is driven by a pair ofpulse motors, each of which moves a different distance when actuated bya driving pulse. The two motors are mechanically coupled so that theirrespective movements are added together. A control system is providedfor permitting the pulse motors to be selectively driven so that theresolution of the system can be adjusted, where resolution is defined asthe movement of the work table for each driving pulse applied to thesystem. The control system includes decoding equipment for properlyselecting resolution commands from input numerical instruction words,and a network of logic gates for appropriately driving the two pulsemotors in response to a particular resolution command.

6 Claims, 4 Drawing Figures PATENTEUSEP 4m 3,757,192

SHEET 1 BF 3 Fig.2

Fig.l

INVENTORS HIROAKI ASANO TSUYOSHI KOIDE TAISUKE KAWAMATA ATTORNEYSPATENTEU 41975 3.757.192

SHEET 2 or 3 Fig.3

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INVENTORS HIROAKI :ASANO TSUYOSHI KOIDE TAISUKE KAWAMATA ATTORNEYSPAIENTEI] SEI' M975 SHEET 3 BF 3 Fig-4 FROM THE COUNTE R104 I FROM THEDECODERIOZ' REGISTER DISCRIM INATOR u I: I

DIRECTION REGISTER RESOLUTION REGISTER N1-N 4 DISCRIMINATOR T0 T HEPULSEGENERATORIOS TO THE LOGIC GATE CIRCUIT PLURAL STEPPING MOTOR NUMERICALFEED CONTROL DEVICE BACKGROUND OF THE INVENTION 1. Field Of TheInvention The present invention relates to a numerical feed controldevice in which the resolution, namely, the distance of movement of amovable member per one pulse, is easily changeable.

2. Description Of The Prior Art Heretofore, in conventional feed devicesfor moving a movable member, such as a slide table, a cross slide, orthe like, the same was moved by two pulse motors each of which rotatedin the same direction and had to be independently utilized. Thus, in thepast, one of the pulse motors could be independently utilized to providea rapid feed of the movable member and the other pulse motor could beindependently utilized to provide a slow or finishing feed. Whilesomewhat satisfactory, with the above described numerical feed controldevice, only one resolution could be realized for the rapid and slowfeed movements and as a result thereof, many inconveniences in operationwould occur. Moreover, in the past, since the pulse motor for providinga rapid feed required a large resolution, the same had to be large insize because of the requirement of large output torque and largeallowable load inertia, and was further found to have poor sensitivityat high frequencies.

SUMMARY OF THE INVENTION Accordingly, it is an object of the presentinvention to provide a new and improved unique numerical feed controldevice in which a movable member is moved by a pair of pulse motorswhich are relatively small in size.

Another object of the present invention is to provide a new and improvednumerical feed control device for controlling the rotational directionor stopping of a pair of pulse motors, wherein the resolution is easilychanged by means of simultaneously changing the rotational directionsand stopping of the pair of pulse motors.

Briefly, in accordance with this invention, the foregoing and otherobjects are, in one aspect, attained by the provision of a numericalfeed control device having a pair of pulse motors for moving a movablemember in a given direction and wherein control circuitry is providedfor enabling the resolution of the device to be easily changed bysimultaneously enabling the direction of rotation and stopping of themotors to be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS The foregoing and other objects of thepresent invention will become more fully apparent from the followingdescription of preferred embodiments of the present invention, withreference to the accompanying drawings, in which:

FIG. 1 is a partial sectional view of a table feed device in accordancewith the present invention;

FIG. 2 is a block diagram of a preferred embodiment of a numericalcontrol system in accordance with the present invention;

FIG. 3 is a block diagram of an alternative and preferred embodiment ofthe control system in accordance with the present invention; and,

FIG. 4 is a block diagram of a typical main control circuit for use inthe embodiment of FIG. 2.

DETAILED DESCRIPTION OF THE INVENTION Referring now to the Drawings,wherein like reference numerals designate identical, or correspondingparts throughout the several views, and more particularly to FIG. 1thereof, wherein a table feed device is shown for enabling a movablemember to move the table thereof in a particular direction, such, forexample, as that defined as the X axis. The table feed device comprisesa machine bed 1 having a table 2 slidably mounted thereon. It should beunderstood that on the table 2, workpieces, machine tools, or the likemay be readily mounted. A reversible pulse motor PM1 is mounted on theright end of the bed 1 through a conventional reduction gear device 3. Afeed screw shaft 4 which is connected to the reduction gear device 3 isrotatably journalled on the bed 1 through anti-friction ball bearings 5.The shaft 4 is operatively engaged with a feed nut assembly 6 which isrotatably mounted within the table 2 through anti-friction ball bearings7. Another reversible pulse motor PM-2 is mounted on the table 2 througha conventional reduction gear device 8 and the output shaft thereofcarries a worm 9. The worm 9 is engaged with a worm wheel 10 which isconcentrically keyed to the feed nut assembly 6. With the abovearrangement, the table 2 can be moved in the leftward and rightwarddirections on the bed 1 by rotation of either or both of the pulsemotors PM-l and PM-2. An extensible bellows 11 is secured between thebed 1 and the table 2 to prevent dirt and other foreign matters frominterfering with the feed movement of the shaft 4 or other members. Inthe embodiment shown, a clockwise rotation of each of the pulse motorswill cause the table 2 to move in a leftward or forward direction asshown in FIG. 1 by a symbol Similarly, a counterclockwise rotation ofeach of the pulse motors will cause the table 2 to move in an oppositeor rightward direction as shown in FIG. 1 by a symbol The resolution,which is defined as the distance of movement of the table 2 for eachpulse applied to the pulse motors PM-l and PM-2, will be referred tohereinafter by the respective reference letters A and B. Moreover, inthe present embodiment, it may be assumed by way of example that theresolution A is larger than the resolution B. Thus, for example, theresolution A may be set to a numeral value of 0.06 mm/pulse, and theresolution B may be set to a numeral value 0.04 mm/pulse.

Referring now to FIG. 2, a first embodiment of a control system,according to the present invention, for controlling the feed speed rateof the table 2 will be described. In FIG. 2, a conventional reader 101is provided for sensing stored command infonnation, such as may beplaced upon punched tape or the like (not shown) and the same isconnected to a conventional decoder 102 for decoding the commandinformation. The decoder 102 is connected to a counter I04 and a maincontrol circuit 103 which is provided for controlling the rotation ofthe pulse motors. The main control circuit 103 is shown in detail inFIG. 4.

Referring again to FIG.-2, the output terminals of the main controlcircuit 103 which are designated Pl through P4 are for selecting aparticular command of resolution N1 through N4 (explained in detailhereinafter) and the same are respectively connected to the AND gatesA1,A4, A7, and A10,A3 and A6,A9 and A12, and A2,A5,A8, and A11.

The output terminals of the main control circuit 103 which aredesignated C1 and C2 are for determining the direction of rotation ofthe respective pulse motors PM-1 and PM-Z, and the same are respectivelyconnected to the AND gates A1,A2,A3,A7,A9, and A11, and A4,A5,A6,A8,Al0,and A12. The output terminal of the main control circuit 103 which isdesignated CX is for determining direction of movement of the table 2along the X-axis andthe same is connected to the AND gates A13 throughA16. The AND gates A1,A2, and A3 are connected to a terminal 1 11 ofadriving circuit DU-1 for defining the clockwise rotation of the pulsemotor PM-1 through the OR GATE R1 and the AND gate A13. The AND gatesA4,A5, and A6 are connected to a terminal 112 of the driving circuitDU-1 for defining the counterclockwise rotation of the pulse motor PM1through the OR gate R2 and the AND gate A14. In a similar manner, theAND gates A7,A8, and A9 and A10,A11 and A12 are respectively connectedto terminals 113 and 114 of a driving circuit DU-2 for defining theclockwise and counterclockwise rotation of the pulse motor PM-2 throughrespective OR gates R3 and R4 and respective AND gates A15 and A16. Itshould be understood that the pulse motors (PM-1, PM-Z) and the drivers(DU-1, DU-2) are conventional units and may be, for example, of the typemanufactured by Fujitsu, Ltd. of Kawasaki, Japan, and sold,respectively, as Type EI-IPM 1-SSS and FANUC 613. The pulse generator105 is connected to the AND gates A13 through A16 and to the counter104. It should be further understood that the counter 104 is connectedto the pulse generator 105 for providing a stopping signal and to themain control circuit 103 for providing a resetting signal.

The above-mentioned term selecting a particular command of resolution"means selecting a command for either or both of the pulse motors PM-1and PM-2, the command telling which motor is to be driven and thedirection of rotation thereof. In accordance with the command selection,the table 2 will move a given distance for each pulse applied to eitheror both of the pulse motors PM-1 and PM-2.

Referring now to FIG. 4, the main control circuit 103 is shown asincluding a register 201 connected to the decoder 102; a discriminator202 connected to a register 201; a resolution register 203, a directionregister 204, an axis register 205, and a feed speed register 206 whichare connected to the discriminator 202; and N1-N4 discriminator 207 andan F1FN discriminator 208 which are respectively connected to theregisters 203 and 206; anda reset circuit 209 connected to the registers203, 204, 205, and 206. The discriminator 207 is connected to outputterminals P1, P2, P3 and P4, and the registers 204 and 205 are,respectively, connected to the output terminals (C1 and C2) and Cx.These terminals are in turn connected to a logic gate circuit whichincludes AND gates A1 through A16 and OR gates R1 through R4, as shownin FIG. 2. The discriminator 208 is connected to a pulse generator 105.The above mentioned references Fl-FN designate the feed speed rate ofthe table 2 of FIG. 1.

It should be understood that while the reader 101 and the decoder 102 ofFIG. 2 and the registers 201, 203, 204, 205 and 206, and thediscriminators 201, 207 and 208 of FIG. 4 have been shown in block form,that these components are conventional and well known to those ofordinary skill in the art.

Having now fully described the manner in which the various components ofthe control device of the present invention are interconnected, themanner in which the present invention operates will now be described indetail. Initially, an information command in the format F1X+5000N1CR,which is stored on the punched tape or the like (not shown) is read bythereader 101, and then sent to the decoder 102 for decoding the punchedinformation therefrom. The above mentioned exemplary information formatF1 X+5000N1CR indicates the following:

F1 designates the feed speed rate of the table 2, or,

in other words, the rate of pulses emitted from the pulse generator Xdesignates movement along the X-axis which is one of the operating axesof the machine tool;

+ designates that a forward movement of the table 2 is desired;

5000 designates the number of pulses to be applied to the pulse motor(s)and hence the desired moving distance of the table 2;

N1 designates the selection of a particular resolution command; and,

CR designates the end of a block of information.

In the above described decoded information, it should be understood thatthe numeral information 5000" is sent to the counter 104 and storedtherein. The other information is sent to the main control circuit 103for providing 1" logic level signals at the respective output terminalsthereof. In other words, the decoded information, with the exception ofthe numeral information 5000, is sent to the discriminator 202 of FIG. 4through the register 201 for permitting separation and appropriatechanneling of the different portions of the input command. Accordingly,the feed rate information F1 is sent to the Fl-FN discriminator 208 fordecoding the suffix numeral value 1, and then sent to the pulsegenerator 105. The axis and direction of movement commands X and aresent to the terminals C1 and Cx. The resolution command N1 is sent tothe Nil-N4 discriminator 207 for decoding the sufi'ix numeral value 1,and then sent to the terminal P1. Upon receipt of the information N1 andthe l logic level signals will be respectively apliedlrqmthe A'W J lEPlWC1 to h nnstaq t e. AND gates A1,A4,A7, and A10, and A1,A2,A3,A7, A9,and A11. Thus, the AND gates Al and A7, each of which have signalsapplied to both of the input terminals thereof, will provide l logiclevel signals to the inputs of the AND gates A13 and A15 throughrespective OR gates R1 and R3. On the other hand, upon receipt of theinformation X, the l logic level signal will be applied from theterminal CX to the inputs of the AND gates A13,A14,A15, and A16. Now,when the pulse generator 105 receives the infromation CR, pulses will beemitted therefrom and will be applied to the counter 104 and to theinputs of the AND gates A13,A14,A15, and A16. As a result thereof, theAND gates A13 and A15 will be opened and thereby allow pulses from thepulse generator 105 to be applied to the terminals 1 l1 and 1 13 forrotating the pulse motors PM-l and PM2 in a clockwise direction. Theclockwise rotation of the motors PM-l and PM-Z will in turn cause thetable 2 to move in a forward direction in accordance with the combinedrotation of the pair of pulse motors. It should be understood that thecounter 104 will also receive pulses from the pulse generator 105 at thesame time as the terminals 111 and 113 and that these pulses will besubtracted from the stored numeral information 5000 during the forwaredrotation of the pulse motors PM-l and PM-Z. When the number in thecounter 104 reaches a zero value, thereby indicating the receipt of 5000pulses, a first signal will be emitted from the counter and applied tothe pulse generator 105 for stopping the same and a second signal willbe emitted from the counter and applied to the main control circuit 103for resetting the same. Thus, it should be apparent that when thecounter 104 reaches a zero value, the table 2 will stop after havingbeen moved forward a predetermined distance at a desired feed speed.

In the exemplary preferred embodiment described above, the resolutioncommand may be used to select four different resolutions designated bythe letters N1 through N4 in accordance with the operation of the twopulse motors PM-1 and PM-2 for a forward movement of the table 2. Thevarious resolutions N1 through N4 are defined as follows:

N1 designates the combined resolution (A+B), namely, when both pulsemotors are rotated in a clockwise direction.

N2 designates the resolution A, namely, when the pulse motor PM-l isrotated in a clockwise direction and the pulse motor PM-2 is stopped.

N3 designates the resolution B, namely, when the pulse motor PM-2 isrotated in a clockwise direction and the pulse motor PM-2 is stopped.

N4 designates the resolution (A-B), namely, when the pulse motor PM-1 isrotated in a clockwise direction and the pulse motor PM-2 is rotated ina counterclockwise direction.

The four different selection commands for various resolutions as the twopulse motors are rotated clockwise and counterclockwise are clearlyshown in the following table.

TABLE trol circuit 103 similar to that of FIG. 4. The NOR gate R5 has anoutput terminal which is connected to the AND gates A1,A4,A7, and A10.The function of the NOR gate R5 is such that a signal will be derivedtherefrom and applied to the AND gates A1,A4,A7, and A10 only when theNOR gate R5 does not receive any signals from the terminals P2,P3, andP4 of the main control circuit 103. Thus, it can be readily seen thatthe function of the NOR gate R5 is the same as that of the connectingrelationship between the terminal P1 and the AND gates A1,A4,A7, and A10as shown in FIG. 2. The unique advantage of the present embodiment isthat it is not necessary to give an information command N1, namely, theselection of a command of resolution N1 on the punched tape or the like.As such, with only three kinds of selection commands of resolution, fourdifferent table movements may be realized in a given moving direction.

It should now be apparent that the present invention relates to animproved numerical feed control device moving a movable member in eithera forward or backward direction at a desired feed speed rate wherein adesired resolution, according to working conditions or finishingaccuracy, is easily selected from various resolutions by means of asimple information command.

Obviously, many modifications and variations of the present inventionare possible in light of the above teachings. Thus, for example,although the control system according to the present invention has beendescribed as a single axis (X axis) control system, it is to beunderstood that any number of axes, such as X,Y,Z, may be controlleddepending upon the command information used. Moreover, while in thepresent embodiments two pulse motors have been used, it is to be un-'derstood that any desired number of pulse motors may be utilized to movea movable member such as a slide table, a cross slide, or the like of amachine tool.

While the invention has been described by means of a specificembodiment, it should be understood that the Operating axis X Tablemoving directions. Forward Backward Solvction ol'n command ofresolution. N1 N2 N3 N4 N1 N2 N3 N4 Rotational direction of the pulsemotor:

IM-l (1W (1W SI (1W (CW ((JW ST ((W IM-- Z CW ST (W CCW C(JW S'I (.CW WResolution A+B A B A-B (A+B) A ll (Al3) NoTi-:.--- (1W:dvsignatus :iclockwise rotation of tho pulsv motors: ((.W=dvsignnl0s uvountvrvlockwisc rotation ol'tho pulse motors; and, SIwiosignntos thestopping of a pulse inolor.

From the above, it can be seen by way of example that if the resolutionsA and B are given the respective numerical values 0.06 mm/pulse and 0.04mm/pulse, then the selection of a command of resolution N1, N2, N3, orN4 will provide the respective numerical values 0.1 mm/pulse, 0.06mm/pulse, 0.64 mm/pulse, and 0.02 mm/pulse for a given direction ofmovement of the table 2.

Referring now to FIG. 2, a second preferred and alternative embodimentof a control system for a table feed device in accordance with thepresent invention is shown with the overall structure being basicallysimilar to that of the embodiment of FIG. 2. In FIG. 3, the referenceletter R5 designates a conventioal NOR gate having a plurality of inputterminals which are con- -nected to the terminals P2, P3, and P4 of amain connovel characteristics of the invention may be incorporated inother structural forms without departing from the spirit and scope ofthe invention as defined in the following claims.

What is claimed as new and desired to be secured by Letters Patent ofthe United States is:

1. A numerical feed control device comprising: at least one movablemember slidably mounted on a machine tool; first and second pulse motorsfor moving said movable member, said first pulse motor having a firstresolution and siad second pulse motor having a second resolutiondifferent from said first resolution, wherein resolution is defined asthe distance of movement of said movable member for each pulse appliedto one of said motors;

'7 engaging means for operatively engaging said pulse motors with saidmovable member; and, a control circuit connected to said pulse motorsfor controlling the rotation thereof, said control circuit comprisingfirst control means for synchronously a rotating both said pulse motorsin one direction, second control means for selectively rotating eitherone of said pulse motors in one direction and stopping the otherthereof, and third control means for rotating one of said pulse motorsin said one direction and for synchronously rotating the other thereofin the reverse direction, whereby four separate resolutions are obtainedby operating said first and second pulse motors individually and byadditively and subtractively combining said first and second resolutionsby means of said first, second, and third control means.

2. A numerical feed control device as set forth in claim ll, whereinsaid engaging means comprises a feed screw shaft connected with one ofsaid pulse motors which is mounted on said machine tool;

a nut member rotatably mounted on said movable member and operativelyengaged with said feed screw shaft;

a worm mounted on the other pulse motor which is mounted on said movablemember; and,

a worm wheel concentrically keyed to said nut member and operativelyengaged with said wheel,

whereby said movable member is moved by means of said pulse motors.

3. A numerical feed control circuit as set forth in claim 1, whereinsaid control circuit further comprises reader for reading inputinformation;

a decoder connected to said reader for decoding said input information;

a main control circuit connected between said decoder and said first,second, and third control means; and,

a pulse generator connected to said main control circuit and to saidpulse motors through said first, second, and third control means,whereby said pulse motors are selectively rotated in response to saidinput information through said first, second, and third control means.

4. A numerical feed control device as set forth in claim 3, wherein saidfirst, second, and third control means include a plurality of AND gatesand OR gates.

5. A numerical feed control device as set forth in claim 4, wherein saidfirst, second, and third means further include a NOR gate.

6. A numerical feed control device as set forth in claim 3, wherein saidcontrol circuit still further includes a counter for stopping said pulsegenerator and resetting said main control circuit upon the reaching of apredetermined count.

1. A numerical feed control device comprising: at least one movablemember slidably mounted on a machine tool; first and second pulse motorsfor moving said movable member, said first pulse motor having a firstresolution and siad second pulse motor having a second resolutiondifferent from said first resolution, wherein resolution is defined asthe distance of movement of said movable member for each pulse appliedto one of said motors; engaging means for operatively engaging saidpulse motors with said movable member; and, a control circuit connectedto said pulse motors for controlling the rotation thereof, said controlcircuit comprising first control means for synchronously rotating bothsaid pulse motors in one direction, second control means for selectivelyrotating either one of said pulse motors in one direction and stoppingthe other thereof, and third control means for rotating one of saidpulse motors in said one direction and for synchronously rotating theother thereof in the reverse direction, whereby four separateresolutions are obtained by operating said first and second pulse motorsindividually and by additively and subtractively combining said firstand second resolutions by means of said first, second, and third controlmeans.
 2. A numerical feed control device as set forth in claim 1,wherein said engaging means comprises a feed screw shaft connected withone of said pulse motors which is mounted on said machine tool; a nutmember rotatably mounted on said movable member and operatively engagedwith said feed screw shaft; a worm mounted on the other pulse motorwhich is mounted on said movable member; and, a worm wheelconcentrically keyed to said nut member and operatively engaged withsaid wheel, whereby said movable member is moved by means of said pulsemotors.
 3. A numerical feed control circuit as set forth in claim 1,wherein said control circuit further comprises a reader for readinginput information; a decoder connected to said reader for decoding saidinput information; a main control circuit connected between said decoderand said first, second, and third control means; and, a pulse generatorconnected to said main control circuit and to said pulse motors throughsaid first, second, and third control means, whereby said pulse motorsare selectively rotated in response to said input information throughsaid first, second, and third control means.
 4. A numerical feed controldevice as set forth in claim 3, wherein said first, second, and thirdcontrol means include a plurality of AND gates and OR gates.
 5. Anumerical feed control device as set forth in claim 4, wherein saidfirst, second, and third means further include a NOR gate.
 6. Anumerical feed control device as set forth in claim 3, wherein saidcontrol circuit still further includes a counter for stopping said pulsegenerator and resetting said main control circuit upon the reaching of apredetermined count.